Oxidative Stability of Vacuum-Packed Chicken Wings Marinated with Fruit Juices during Frozen Storage

The fresh skin-on chicken wings (Cobb 500) were obtained from a local market in Badulla, Sri Lanka. The chicken wings were immediately transported to the laboratory in a polystyrene box containing ice, washed with tap water, drained and stored at –18°C until further use.

Moderately ripened mangoes (Mangifera indica; Willard variety), pineapples (Ananas comosus; Mauritius variety), and June plums (Spondias dulcis; Tall variety) were obtained from local farmers in Sri Lanka for the preparation of marinades. On the day of the analysis, each type of fruit was manually peeled, washed with tap water, cut into pieces, chopped and strained to obtain fruit juices. Marinades were then prepared separately by mixing 60% of fruit juice, 37% of water and 3% of salt and filled into food grade plastic bottles. Chicken wings were tumbled separately in the marinades at 1:1 ratio for 30 min, subdivided into marination holding times (12 and 24 h) and finally kept at 4°C. Raw chicken wings were used as the control. After each marination period, chicken wings from different marinades were vacuum-packed separately and stored under frozen storage (–18°C). Three best marinade-time combinations were selected based on the results of a sensory evaluation and wings marinated with such combinations were used for weekly determination of pH, water holding capacity (WHC), 2-thiobarbituric acid reactive substances (TBARS) and 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) values (Choe et al., 2020; Lee et al., 2021). Before analyses, the frozen marinated chicken wings were thawed overnight at 4°C.

Fruit juices were analyzed for antioxidant activity using DPPH free radical scavenging assay according to the method described by Choe et al. (2020) with slight modifications. Methanolic DPPH stock solution (0.1 mM) was prepared by dissolving 10 mg of DPPH powder in 125 mL of methanol. After that, 5 mL of fruit juice was mixed with 80% methanol and kept in a shaker for 30 min at room temperature. The mixture was then centrifuged (ST 40R, Thermo Fisher Scientific, Osterode, Germany) at 1,409×g for 10 min at 4°C and 200 μL of the supernatant was mixed with 1 mL of DPPH solution. The mixture was shaken well and kept to stand in a dark place for 30 min at room temperature. The absorbance of mixtures was read at 517 nm using a spectrophotometer (UV-2005, J.P. Selecta, Barcelona, Spain). The readings were compared with the control prepared with 200 μL of 80% methanol and 1 mL of DPPH. The scavenging activity was calculated using the following equation.

Fruit juices were analyzed for total phenolic content using Folin-Ciocalteu method as described by Singleton et al. (1999) with slight modifications. First, 5 mL of each fruit juice was mixed with 80% methanol and kept in a shaker for 30 min at room temperature. The mixture was then centrifuged (ST 40R, Thermo Fisher Scientific) at 1,409×g for 10 min at 4°C. Supernatant (1 mL) and standard solution of gallic acid (10, 20, 40, 60, 80, and 100 μg/mL) were mixed separately with 1 mL of Folin- Ciocalteu reagent. After 5 min, the mixture was added with 10 mL of 7% Na₂CO₃ and incubated for 90 min at room temperature. The absorbance was measured at 750 nm using a spectrophotometer (UV-2005, J.P. Selecta). Total phenolic content of each fruit juice was reported as μg gallic acid equivalent (GAE)/mL.

The design of the sensory evaluation for marinated chicken wings was reviewed and approved by the Research Ethics Review Committee of Uva Wellassa University (No. UWU/REC/2021/002). Marinated chicken wings thawed overnight at 4°C were first cooked at 150°C for 30 min in an electrical oven. Cooked wing samples were then prepared to uniform size (1.5 cm×2 cm), wrapped in aluminum foil to preserve the aroma and prevent moisture loss, and kept in a drying oven (DHG-9145A, Zenith Lab, Changzhou, China) at 60°C until sensory evaluation. Thirty untrained panelists participated in the sensory evaluation in individual booths. The sensory properties such as color, odor, flavor, taste, juiciness, tenderness and overall acceptability were evaluated using a 7-point hedonic scale. Drinking water at room temperature was provided to the panelists to cleanse their mouth prior to and between sample evaluations. Three best marinade-time combinations were selected based on the results of this sensory evaluation for further analysis.

Uptake of marinade by chicken wings was determined as described by Fenton et al. (1993) and Klinhom et al. (2015) with slight modifications. The weights of the chicken wings before marination, immediately after tumbling and after each marination holding time were recorded. Excess marinades were removed from the chicken wing surfaces before weighing. The uptake of marinades was calculated using the following equation.

Marinade loss of chicken wings was calculated according to the protocol of Fenton et al. (1993) using the following equation.

WHC of chicken wing was determined based on the technique of Hamm (1961), as described by Wilhelm et al. (2010). Marinated chicken wing samples (2 g) were carefully placed between two pieces of filter papers (No. 4; Whatman International, Maidstone, UK) on acrylic plates and left under a 10-kg weight for 5 min separately. After recording the final weight of each sample, WHC was calculated using the following equation.

Chicken wing samples (1 g) from each marinade were homogenized separately with 9 mL of distilled water for 60 s by using a homogenizer (T 10 basic Ultra-Turrax, Ika Laboratory Equipment, Korea) and filtered through a filter paper (No. 4, Whatman International). The pH value of each filtrate was determined with a pH meter (pH 700, Eutech Instruments Pte, Singapore) after calibration using buffers (pH 4.01, 7.00, and 10.01) at room temperature.

TBARS values of marinated chicken wings were analyzed using the method described by Lee et al. (2021) with some modifications. Chicken wing samples (5 g) were homogenized in 15 mL of deionized water using homogenizer (D-500, Velp Scientifica, Usmate, Italy) at 14,000 rpm for 30 s. Butylated hydroxytoluene (BHT; 50-μL) (7.2% w/v in ethanol) and thiobarbituric acid/trichloroacetic acid solution (20 mM TBA and 15% [w/v] TCA; 2 mL) were added to the homogenate (1 mL) and vortexed for 30 s. The mixture was then incubated in a water bath (YCW-010E, Gemmy Industrial, Taipei, Taiwan) at 90°C for 30 min, and subsequently cooled for 10 min in an ice-water bath. After centrifuging the samples at 1,409×g for 15 min (5°C) using a ST 40R centrifuge (Thermo Fisher Scientific), the absorbance of was measured at 532 nm with a UV-2005 spectrophotometer (J.P. Selecta) against a blank prepared with 1 mL deionized water and 2 mL TBA/TCA solution. The malondialdehyde (MDA) concentration of each sample was determined against an external standard curve constructed using tetraethoxypropane. The results were expressed as mg MDA per kg of marinated chicken wings.

DPPH free radical scavenging activity of the marinated chicken wings was measured using methods described by Choe et al. (2020) with slight modifications. Chicken wing samples (1 g) were mixed with 80% methanol and homogenized Mixtures were then kept in a shaker for 30 min at room temperature and centrifuged (ST 40R, Thermo Fisher Scientific) at 1,409×g for 10 min at 4°C. The same analytic procedure was followed as described in antioxidant activity of fruit juice section.

The complete experiment was repeated three times in a completely randomized design and duplicate samples were drawn for each parameter. The data were subjected to one-way analysis of variance (ANOVA) and Tukey’s comparison of the means test (p≤0.05) using Minitab 17 software. Data obtained from sensory analysis was analyzed using the Friedman test.

The antioxidant activity and total phenolic content of fruit juices used in marinades are shown in Fig. 1. The highest antioxidant activity in terms of DPPH free radical scavenging activity was shown by mango and pineapple juices (p<0.05) while the total phenolic content of mango juice was significantly higher than that of other fruit juices tested in the present study. Antioxidant activity of mango varieties has previously been proven by various researchers. According to Umamahesh et al. (2016), mango contains high amount of antioxidants compared to other fruits. Both mango peel and kernel have been shown to be rich sources of antioxidant constituents such as gallates, flavonols, carotenoids, ascorbic acids, and xanthone glucosides (Ajila et al., 2007) which are considered as natural radical terminators. Furthermore, Arogba and Omede (2012) found that mango possesses high radical scavenging activity due to the presence of high levels of flavonoids and phenolic acids. Different cultivars of pineapple have exhibited different levels of antioxidant activity owing to the presence of carotenoids, vitamin C and phenolic compounds (Ferreira et al., 2016).

Fig. 1. Antioxidant activity (AOA) and total phenolic content (TPC) of fruit juices used in marinades. ^a,b Values with different letters differ significantly (p<0.05).

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Sensory analysis results of marinated chicken wings are presented in Table 1. Marination affected the flavor, taste and overall acceptability of the samples as judged by the sensory panel (p<0.05). Accordingly, chicken wings marinated for 24 h in pineapple juice received the highest scores for overall acceptability, taste and flavor attributes followed by those marinated for 12 h in June plum, and 24 h in mango juice compared to control samples (p<0.05). Considering these results, aforementioned three marinade-time combinations were selected for further analysis.

Uptake of marinade and marinade loss in chicken wings assessed under selected marinade-time combinations are shown in Fig. 2. Accordingly chicken wings marinated for 24 h in mango juice had the highest uptake of marinade compared to other marinade-time combinations (p<0.05). In addition, the highest marinade loss was reported in chicken wings marinated for 12 h in June plum juice. The observed results might be attributed to the fact that high fiber content of mango could support to increase WHC of marinated meat (Roidoung et al., 2020).

Fig. 2. Marinade loss and marinade uptake of chicken wings after marinating with different fruit juices. ^a–c Different letters between treatments are statistically different (p<0.05).

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The changes in pH values of vacuum-packed marinated chicken wings over frozen storage are depicted in Table 2. Chicken wings marinated with June plum for 12 h showed the lowest pH values throughout the storage period (p<0.05) while the highest pH values were observed in control chicken wings. Decreases in pH values of all marinated chicken wings were reported over the storage period and it could be attributed to the acidity of fruit juices (Emanuel et al., 2012).

Table 3 shows the changes in WHC of vacuum-packed marinated chicken wings over frozen storage. WHC of the marinated chicken wings from all treatments was significantly decreased over the storage period. Barbut (1993) reported that lower muscle pH was associated with lower WHC. Hence, the decreased WHC over frozen storage can be attributed to the lower muscle pH reported during the storage which results in denaturation of myofibrilar and sarcoplasmic proteins (Olivo et al., 2001). The lowest WHC throughout the storage was observed in chicken wings marinated with mango juice for 24 h (p<0.05) whereas the highest WHC throughout the storage was reported in the chicken wings marinated with pineapple juice for 24 h (p<0.05). In previous studies, a reduction in WHC has been reported in enzymatically tenderized meat such as bromelain treated meat due to the changes occur in myofibrillar protein structure (Istrati et al., 2012). However, Manohar et al. (2016) observed a gradual increase in WHC of the meat as the bromelain concentration increased.

Lipid oxidation is considered as the primary process responsible for quality deterioration during storage mainly due to its negative impact on flavor, color, texture, and nutritional value (Kim et al., 2013). To investigate the effect of marinades containing different fruit juices on the lipid oxidation of chicken wings, TBARS values of vacuum-packed marinated chicken wings were measured over a 4-wk frozen storage (Table 4). Over the storage period, the lowest TBARS values were reported in chicken wings marinated with mango juice for 24 h followed by those marinated with pineapple juice for 24 h and June plum juice for 12 h, respectively (p<0.05). This finding is supported by the highest antioxidant activity and total phenolic contents detected in mango juice during this study (Fig. 1). TBARS values of the marinated chicken wings were significantly increased over the storage period irrespective of the marinade used, however within the acceptable limits. Domínguez et al. (2019) stated that lipid oxidation in meat and meat products are influenced by storage time; with increasing time the possibility of radicals to cause damage to lipids increases. In addition, the release of iron from heme-proteins gets accelerated with long storage periods and it catalyzes multiple reactions in the initiation and propagation phases of lipid oxidation.

DPPH free radical scavenging activity of marinated chicken wings over the frozen storage period is shown in Table 5. Vacuum packed chicken wings marinated with mango juice for 24 h had a significantly higher DPPH free radical scavenging activity throughout the storage period compared to those marinated with other two marinades and control. DPPH free radical scavenging activity of marinated chicken wings was significantly decreased with the storage, irrespective of the fruit juice used in marinades. Interestingly, DPPH free radical scavenging activity of all the marinated chicken wings was more than 2 folds higher than that of the control. Both mango and pineapple are considered as rich sources of dietary antioxidants such as amino acids, carotenoids, and phenolic compounds (Arampath and Dekker, 2021) while June plums are good sources of ascorbic acids, and phenolic compounds (Jayarathna et al., 2020). The findings of the present study on DPPH free radical scavenging activity of marinated chicken wings can also be confirmed by the highest antioxidant activity and total phenolic contents detected in mango juice during this study (Fig. 1).